Thought disorder

A thought disorder (TD) is a multifaceted construct that reflects abnormalities in thinking, language, and communication. Thought disorders encompass a range of thought and language difficulties and include poverty of ideas, perverted logic (illogical or delusional thoughts), word salad, delusions, derailment, pressured speech, poverty of speech, tangentiality, verbigeration, and thought blocking.

Two subcategories of thought disorder are content-thought disorder, and formal thought disorder. CTD has been defined as a thought disturbance characterized by multiple fragmented delusions. A formal thought disorder is a disruption of the form (or structure) of thought.

Also known as disorganized thinking, FTD affects the form (rather than the content) of thought. (including mood disorders, dementia, mania, and neurological diseases). Unlike hallucinations and delusions, it is an observable, objective sign of psychosis. It reflects a cluster of cognitive, linguistic, and affective disturbances that have generated research interest in the fields of cognitive neuroscience, neurolinguistics, and psychiatry. Disturbances of thinking and speech, such as clanging or echolalia, may also be present in Tourette syndrome; other symptoms may be found in delirium. A clinical difference exists between these two groups. Patients with psychoses are less likely to show awareness or concern about disordered thinking, and those with other disorders are aware and concerned about not being able to think clearly.

Content-thought disorder

Thought content is the subject of a person's thoughts, or the types of ideas expressed. Mental health professionals define normal thought content as the absence of significant abnormalities, distortions, or harmful thoughts.

A person's cultural background must be considered when assessing thought content. Abnormalities in thought content differ across cultures. Specific types of abnormal thought content can be features of different psychiatric illnesses.

Examples of disordered thought content include:

Suicidal ideation: thoughts of ending one's own life.
Homicidal ideation: thoughts of ending the life of another.

Preoccupation: excessive and/or distressing thoughts that are stressor-related and associated with negative emotions.
Obsessive–compulsive disorder: As obsession, repeated intrusive thoughts that are inappropriate, and distressing or upsetting, and compulsive behavior repeated actions as an attempt to rid the intrusive thoughts.

Formal thought disorder (FTD), also known as disorganized speech or disorganized thinking, is a disorder of a person's thought process in which they are unable to express their thoughts in a logical and linear fashion. The Kiddie Formal Thought Disorder Rating Scale (K-FTDS) can be used to assess the presence of formal thought disorder in children and their childhood. Although it is very extensive and time-consuming, its results are in great detail and reliable.

Nancy Andreasen preferred to identify TDs as thought-language-communication disorders (TLC disorders). Up to seven domains of FTD have been described on the Thought, Language, Communication (TLC) Scale, with most of the variance accounted for by two or three domains. Clinical psychologists typically assess FTD by initiating an exploratory conversation with a client and observing their verbal responses.

FTD is often used to establish a diagnosis of schizophrenia; in cross-sectional studies, 27 to 80 percent of patients with schizophrenia present with FTD. A hallmark feature of schizophrenia, it is also widespread amongst other psychiatric disorders; up to 60 percent of those with schizoaffective disorder and 53 percent of those with clinical depression demonstrate FTD, suggesting that it is not exclusive to schizophrenia. About six percent of healthy subjects exhibit a mild form of FTD. The FTD present in patients with schizophrenia was characterized by disorganization, neologism, and fluid thinking, and confusion with word-finding difficulty. The most comprehensive longitudinal study of FTD by 2023 found a distinction in the longitudinal course of thought-disorder symptoms between schizophrenia and other psychotic disorders. The study also found an association between pre-index assessments of social, work and educational functioning and the longitudinal course of FTD.

Possible causes

Several theories have been developed to explain the causes of formal thought disorder. It has been proposed that FTD relates to neurocognition via semantic memory.

FTD in schizophrenia has been found to be associated with structural and functional abnormalities in the language network, where structural studies have found bilateral grey matter deficits; deficits in the bilateral inferior frontal gyrus, bilateral inferior parietal lobule and bilateral superior temporal gyrus are FTD correlates.

The origins of FTD have been theorised from a social-learning perspective. Singer and Wynne said that familial communication patterns play a key role in shaping the development of FTD; dysfunctional social interactions undermine a child's development of cohesive, stable mental representations of the world, increasing their risk of developing FTD.

Treatments

Antipsychotic medication is often used to treat FTD. Although the vast majority of studies of the efficacy of antipsychotic treatment do not report effects on syndromes or symptoms, six older studies report the effects of antipsychotic treatment on FTD. These studies and clinical experience indicate that antipsychotics are often an effective treatment for patients with positive or negative FTD, but not all patients respond to them.

Cognitive behavioral therapy (CBT) is another treatment for FTD, but its effectiveness has not been well-studied. However, provisional evidence suggests that FTD may not preclude the effectiveness of CBT. They can also occur in schizophrenia and other disorders (such as mania or depression), or in anyone who may be tired or stressed. To distinguish thought disorder as a mental health condition, professionals may consider patterns of speech, the severity and frequency of symptoms, and any resulting functional impairment. FTD is a hallmark feature of schizophrenia, but is also associated with other conditions that can cause psychosis (including mood disorders, dementia, mania, and neurological diseases). Under SANS, thought blocking is considered a part of alogia, and so is increased latency in response.

Circumstantial speech (also known as circumstantial thinking): An inability to answer a question without providing excessive, unnecessary or irrelevant detail. Circumstantial speech eventually reaches a relevant point, unlike in tangential speech.
Clanging: instances in which ideas are related only by phonetics (similar or rhyming sounds) rather than actual meaning. This may present as excessive rhyming or alliteration ("Many moldy mushrooms merge out of the mildewy mud on Mondays", or "I heard the bell. Well, hell, then I fell"). It is most commonly seen in the manic phase of bipolar disorder, although it is also often observed in patients with schizophrenia and schizoaffective disorder.
Derailment (also known as loosening of associations and knight's move thinking):
Echolalia: Echoing of another's speech,
Evasion (also known as paralogia and perverted logic): The next logical idea in a sequence is replaced with another idea closely related to it, but inappropriate to the current conversational context.
Flight of ideas: Conclusions are reached which do not follow logically (non sequiturs or faulty inferences). "Do you think this will fit in the box?" is answered with, "Well of course; it's brown, isn't it?"
Incoherence (word salad): Although neologisms may refer to words formed incorrectly whose origins are understandable (such as "headshoe" for "hat"), these can be more clearly referred to as word approximations.
Overinclusion:
Perseveration:
Pressured speech: Rapid speech without pauses, which is difficult for others to interrupt.
Referential thinking: Viewing innocuous stimuli as having a specific meaning for the self ("What's the time?" "It's 7 o'clock. That's my problem").
Semantic paraphasia: Substitution of inappropriate words ("I slipped on the coat, on the ice I mean, and broke my book").
Stilted speech: ("Where are you from?" "My dog is from England. They have good fish and chips there. Fish breathe through gills").
Thought blocking (also known as deprivation of thought and obstructive thought): An abrupt stop in the middle of a train of thought after which the subject may not be able to continue.
Verbigeration: Meaningless, stereotyped repetition of words or phrases in place of understandable speech; seen in schizophrenia.

Terminology

Psychiatric and psychological glossaries in 2015 and 2017 defined thought disorder as disturbed thinking or cognition which affects communication, language, or thought content including poverty of ideas, neologisms, paralogia, word salad, and delusions (disturbances of thought content and form), and suggested the more-specific terms content thought disorder (CTD) and formal thought disorder (FTD). and a 2002 medical dictionary which generally defined thought disorders similarly to the psychiatric glossaries and used the word in other entries as the ICD-10 did.

A 2017 psychiatric text describing thought disorder as a "disorganization syndrome" in the context of schizophrenia:

The text said that some clinicians use the term "formal thought disorder" broadly, referring to abnormalities in thought form with psychotic cognitive signs or symptoms, and studies of cognition and subsyndromes in schizophrenia may refer to FTD as conceptual disorganization or disorganization factor.

Course, diagnosis, and prognosis

It was believed that TD occurred only in schizophrenia, but later findings indicate that it may occur in other psychiatric conditions (including mania) and in people without mental illness. Not all people with schizophrenia have a TD; the condition is not specific to the disease.

People with schizophrenia have more negative TD, including poverty of speech and poverty of content of speech, but also have relatively high rates of some positive TD. People with depression have relatively-fewer TDs; the most prominent are poverty of speech, poverty of content of speech, and circumstantiality. Andreasen noted the diagnostic usefulness of dividing the symptoms into subtypes; negative TDs without full affective symptoms suggest schizophrenia. FTDs are commonly found in schizophrenia and mood disorders, with poverty of speech content more common in schizophrenia.

Psychoses such as schizophrenia and bipolar mania are distinguishable from malingering, when an individual fakes illness for other gains, by clinical presentations; malingerers feign thought content with no irregularities in form such as derailment or looseness of association.

Autism spectrum disorders (ASD) whose diagnosis requires the onset of symptoms before three years of age can be distinguished from early-onset schizophrenia; schizophrenia under age 10 is extremely rare, and ASD patients do not display FTDs. However, it has been suggested that individuals with ASD display language disturbances like those found in schizophrenia; a 2008 study found that children and adolescents with ASD showed significantly more illogical thinking and loose associations than control subjects.

Rorschach tests have been useful for assessing TD. Hermann Rorschach developed this test to diagnose schizophrenia after realizing that people with schizophrenia gave drastically different interpretations of Klecksographie inkblots from others whose thought processes were considered normal, and it has become one of the most widely used assessment tools for diagnosing TDs. Symptoms of TD are inferred from disordered speech, based on the assumption that disordered speech arises from disordered thought. Although TD is typically associated with psychosis, similar phenomena can appear in different disorders and leading to misdiagnosis.

A criticism related to the separation of symptoms of schizophrenia into negative or positive symptoms, including TD, is that it oversimplifies the complexity of TD and its relationship to other positive symptoms. The three clusters became known as negative symptoms, psychotic symptoms, and disorganization symptoms.

Positive-negative-symptom diametrics, however, may enable a more accurate characterization of schizophrenia.